The hair consists of a shaft, which is the visible part, a hair bulb situated 3 or 4 mm under the scalp surface and a dermal papilla. The shaft consists of 95% keratin, water, fatty acids, melanin and a small quantity of iron and zinc.
The shaft is surrounded by two sheaths: the inner root sheath necessary for hair growth and the outer root sheath having a similar composition to that of the epidermis. They determine the definitive shape of the hair. The outer root sheath particularly hosts the stem cells from which the hair follicle is cyclically regenerated.
On the entire surface thereof, the fibre is protected by a thin layer referred to as the cuticle. It is formed from overlapping colourless cells called scales. Cohesion between these scales is provided by a cement rich in lipids and in ceramides in particular.
The bulb consists of actively dividing keratinocytes to form the hair shaft and the inner and outer root sheaths.
The dermal papilla at the base of the bulb enables hair irrigation and oxygenation and cellular waste disposal. It consists of fibroblasts secreting an important extracellular matrix. Highly vascularised, it is involved in hair nutrition and regulation functions. The papilla can be considered to be the biological motor of the hair.
Hair Life Cycle
Individual hair emerge, grow and fall out according to the independent hair life cycle comprising the following phases.
The anagen phase is the hair growth phase, during which the hair grows from the bulb. Hair matrix cells undergo significant division to form the hair shaft and the inner and outer root sheaths. In the anagen phase, the hair matrix is the site of intense cellular proliferation. The hair shaft is then keratinised. Simultaneously, the hair follicle grows in the deep layers of the skin to nourish the hair. This is the longest period of the hair life cycle, lasting 2 to 5 years on average. The majority of hair is in the anagen phase.
The catagen phase is a resting phase during which the hair stops changing. This phase last approximately 3 weeks.
Finally, during the telogen phase, the hair no longer grows, but remains attached to the hair follicle. At the end of this phase, the old hair falls out, leaving its place for a new follicle in the anagen phase, and the hair life cycle is resumed. During this phase, there is little or no cellular proliferation, and no further hair shaft growth is observed.
If the hair life cycle is normal, the percentage of hair in the anagen phase is between 85 and 90% of all hair, the catagen phase applies to approximately 1% of hair and approximately 10 to 15% of hair is in the telogen phase.
However, during a man or woman's lifetime, for various reasons, the hair life cycle may be subject to abnormal changes. The causes of such changes may particularly be the change of season, fatigue, stress, hormonal imbalance, hair treatment, medication having an effect on hair, pollution or ageing. In this case, the percentage of hair in the anagen phase may fall below 80% of all hair and the hair in the telogen phase may be in a proportion greater than 20% of all hair. The hair loss becomes excessive. This abnormal hair loss is accompanied by weakening of the hair structure.
Similarly, some animals with hair, such as pets, sometimes undergo short- or long-term abnormally excessive hair loss.
Prior Art Solutions
To remedy all or part of this imbalanced hair life cycle problem giving rise to abnormally significant hair loss and weakening of the hair, some medicinal products, cosmetic products or dietary supplements are known.
In particular, active substances of medicinal products such as minoxidil and finasteride (or propecia) are known. These active substances are genuinely effective but involve the drawback of being chemical products, potentially, as for any synthetic molecules, producing adverse side effects in the patient such as irritation or thickening of body hair, among others. Furthermore, finasteride is not recommended for women.
Moreover, dietary supplements based on vitamins and minerals are known, with a claimed effect on the beauty of skin appendages and skin, without particularly targeting an “anti-hair loss” treatment. However, these vitamins and minerals are readily available as part of a varied and balanced diet.
Further dietary supplements containing plant extracts optionally associated with vitamins and minerals exist. They are mostly used traditionally, but without clinical studies proving the efficacy thereof. Examples include pumpkin seed oil, brewer's yeast, green tea, soy isoflavones.
Further dietary supplements only apply to excessive hair loss associated with hormonal imbalance, particularly androgenetic alopecia. For example, this is the case of dietary supplements based on Saw-palmetto. These dietary supplements are essentially intended for men.
A further known dietary supplement, marketed under the brand Priorin® by Bayer, promotes hair growth by supplying the cells with essential nutrients. It contains a whole golden millet and wheat germ oil extract, associated with cystine and an essential vitamin for hair, calcium panthothenate. Wheat germ oil consists of fatty acids such as linoleic acid and vitamin E.
A further dietary supplement marketed under the trade name Hirsana® by Zwicky AG is based on millet oil containing miliacin associated with vitamins and minerals to help stop hair loss and strengthen hair and nails.